Countersinking Setup and Cost
Countersinking adds a $9 minimum to your order. Save up to 70% or more with quantity discounts! We calculate quantity discounts based on several factors including material, operation type, number of operations on each part and number of duplicate parts. Our app will automatically provide quantity discounts based on your order.
Part Sizing
The success of countersinking is heavily dependent upon the material thickness and the size of the part, so we’ve implemented sizing minimums and maximums your part will need to adhere to in order to be countersunk:
Minimum part size of 1” x 4”
- Minimum length of the shortest side is 1”
- Minimum length of the longest side is 4”
Maximum part size of 14” x 46”
- Maximum length of the shortest side is 14”
- Maximum length of the longest side is 46”
Be sure to check our Processing Min/Max chart for more information on minimum and maximum geometry for your specific material, thickness, and part size.
Materials Available for Countersinking
At this time, we offer 7 materials for countersinking:
File Setup and Design Considerations
Confirming countersink placement in our app
When you upload your file to our app, you’ll be able to view your part in a 3D model to check that the final product will function the way you intended. Use this model to make sure your countersinks are placed in the correct orientation on your part. Countersinks can be placed on the top or bottom face of a part, so it’s important to check carefully that they are indicated on the correct face.
Indicating countersunk holes
When setting up your file for countersinking, keep in mind that you only need to include the inner circumference of the hole (called the Minor) that is to be countersunk. Do not include the outer circumference (the size of the countersink, called the Major) in your file as that is what will be cut during the machining process, causing your hole to be too large to countersink. Your file should look like the one indicated here:
Hole size
The Major hole size should be the same size or slightly larger than the diameter of the hardware head you’re using. It’s best to use the exact diameter of the hardware head as your reference, but a good rule of thumb is to make the countersink 50% larger than the internal hole (Minor).
When selecting your hole operations for the desired hole in your design, we will automatically resize the hole to the required size as long as the starting hole is less than .500” in diameter. Please keep in mind that because they will resize, you will need to verify you have adequate clearance to other features and edges of the material.
You can see examples of countersinking sizing in the chart below. It’s important to note that these examples are based on sample hardware (linked in the chart) and hardware specifications and styles will vary based on the manufacturer.
Imperial/SAE Examples:
| Hardware Size | Hardware Head Diameter | Countersink Minor Diameter | Countersink Major Diameter | Countersink Depth |
|---|---|---|---|---|
| 10-32, ⅜” Hex Drive Flat Head Screws | 0.411” | 0.194” | 0.411” | 0.127” |
| ¼-20, ⅜” Hex Drive Flat Head Screws | 0.531” | 0.250” | 0.531” | 0.161” |
Metric Examples:
| Hardware Size | Hardware Head Diameter | Countersink Minor Diameter | Countersink Major Diameter | Countersink Depth |
|---|---|---|---|---|
| M5 x .8mm, 14mm Hex Drive Flat Head Screw | 10mm | 5mm | 10mm | 2.8mm |
| M8 x 1.25mm, 12mm Hex Drive Flat Head Screw | 16mm | 8mm | 16mm | 4.4mm |
Depth and angle
The depth of the countersink should be no more than 60% of the material thickness. Any deeper and you are risking the structural integrity of the material and part. If your countersink needs to exceed that depth, make sure the holes are spaced out far enough away from each other to prevent undue stress. Here, depth is defined as the distance from the surface of the material or top of the cone to the bottom of the cone. This is typically considered the head height for flat head bolt hardware specifications.
The angle of the countersink is dependent upon the hardware being used. Ideally, the hardware has at least 50% contact with the countersunk hole, but it doesn’t have to match exactly. The standard countersink angle for metric hardware is 90°, and the standard countersink angle for imperial hardware is 82°. We offer sizes in both angles.
Sizes available
The “Major” measurement shown here is the larger diameter at the top of the countersink, and the “Minor” measurement is the smaller diameter at the bottom of the countersink where the hole is at its smallest
When selecting your hole operations for the desired hole in your design, we will automatically resize the hole to the required size as long as the starting hole is less than .500” in diameter.
Please keep in mind that because they will resize, you will need to verify you have adequate clearance to other features and edges of the material.
90° (Common for Metric bolts)
| Metric Flat Head Bolt | Major | Minor | Depth |
|---|---|---|---|
| M2 x 0.4mm | 4mm (0.157”) | 2.39mm (0.099”) | .074mm (.029″) |
| M2.5 x 0.45mm | 5mm (0.197”) | 2.49mm (0.103”) | 1.19mm (.047″) |
| M3 x 0.5mm | 6mm (0.236”) | 3.18mm (0.130”) | 1.35mm (.053″) |
| M4 x 0.7mm | 8mm (0.315”) | 4.04mm (0.164”) | 1.93mm (.076″) |
| M5 x 0.8mm | 10mm (0.394”) | 5.00mm (0.202”) | 2.44mm (.096″) |
| M6 x 1mm | 12mm (0.472”) | 6.35mm (0.255”) | 2.77mm (.109″) |
| M8 x 1.25mm | 16mm (0.630”) | 8.00mm (0.320”) | 3.94mm (.155″) |
82° (Common for Imperial/SAE bolts)
| Standard Flat Head Bolt | Major | Minor | Depth |
|---|---|---|---|
| 4-40 | 0.255” (6.48mm) | 0.130” (3.18mm) | .072″ (1.83mm) |
| 6-32 | 0.307” (7.80mm) | 0.164” (4.04mm) | .082″ (2.08mm) |
| 8-32 | 0.359” (9.12mm) | 0.193” (4.78mm) | .095″ (2.41mm) |
| 10-24 | 0.411” (10.44mm) | 0.199” (4.93mm) | .122″ (3.10mm) |
| 10-32 | 0.411” (10.44mm) | 0.199” (4.93mm) | .122″ (3.10mm) |
| 1/4-20 | 0.531” (13.49mm) | 0.255” (6.35mm) | .159″ (4.04mm) |
| 1/4-28 | 0.531” (13.49mm) | 0.255” (6.35mm) | .159″ (4.04mm) |
| 5/16-18 | 0.656” (16.66mm) | 0.318” (8.08mm) | .194″ (4.93mm) |
| 5/16-24 | 0.656” (16.66mm) | 0.318” (8.08mm) | .194″ (4.93mm) |
More details are available from our preferred vendor, McMaster
What to Expect From Finished Parts
- Parts may have oil/lubricant residue on the surface
- Some light deburring may be required by the customer to remove sharp edges left by the countersinking process
- Parts will not have a perfectly machined finish. Some scoring is expected.
- Powder coating will add .002”-.005” (.051mm-0.13mm) per side. We’ll adjust the hole size to account for this, but keep in mind that the fit may be tight on countersinks with powder coating
Pre-flight Checklist
- File is in a format that we accept (2D: .dxf, .dwg, .ai, .eps; 3D: .step or .stp)
- All holes and cutouts are at least 50% material thickness for laser cut parts
- All holes and cutouts are no less than 0.070” for most waterjet cut parts
- All holes and cutouts are no less than 0.125” for all CNC routed parts
- File is built at a 1:1 scale, preferably in inch or mm units
- All objects are on the same layer
- All stray points, duplicate lines, empty objects and text areas have been removed
- No shapes have open contours
- All shapes have been united, combined or merged
- All text has been converted to outlines or paths
- Cut-out text (reversed text) has bridges or has been stencilized
